MILWAUKEE -- One week after losing Matt Garza to a rib-cage injury, Brewers manager Ron Roenicke said he's operating under the assumption that Garza will spend only the minimum 15 days on the disabled list.

"That's what I'm going off of right now," Roenicke said. "Until something happens where I'm led to believe that's not the case, that's my assumption."

Whether that assumption is realistic depends on Garza's progress in the coming days. He has yet to throw a baseball since feeling a muscle grab on the next-to-last pitch of his Aug. 3 start in St. Louis.

Roenicke was not aware of a target date for Garza to resume throwing. Assistant general manager Gord Ash confirmed as much, saying the club's medical staff was "taking a wait-and-see approach."

"He's doing pretty good," Roenicke said. "They've been pushing him with the exercises. A little sore today because of just pushing him, so today is a day that he will not exercise."

Mike Fiers made his first start Saturday in Garza's place and is scheduled to pitch again on Thursday at Wrigley Field. Garza will be eligible for reinstatement beginning Aug. 19.

The Brewers' upcoming schedule is helpful in the event Garza needs more DL time. Because of off-days, the Brewers could align the rotation such that they would not need a fifth starting pitcher after Thursday until Sept. 3.

Fiers became the seventh different pitcher to start a game for the Brewers. Before Saturday, the Brewers and Angels were the only teams in the Majors to get this far into the season with only six starters.

Roenicke said he still feels good about the Brewers' starting-pitching depth.

"We know we'll get Garza back, we know Marco [Estrada] is still down in the bullpen, and if something happens, we still like Marco in there starting," Roenicke said. "So I don't think it's stretched to the point where I say, 'Wow, I don't know where else to go.' We do know where else to go."

Adam McCalvy is a reporter for MLB.com. Read his blog, Brew Beat, and follow him on Twitter at @AdamMcCalvy. This story was not subject to the approval of Major League Baseball or its clubs.